Removal of hydrogen halides from hydrocarbon conversion products



June 4, 1946. G. B. ZIMMERMAN REMOVAL OF HYDROGEN HALIDES FROM HYDROGARBON CONVERSION PRODUCTS Filed July 5, 194s l Y J-zffez for: I 6070,07? ZZzvvzerz/zan process ,Patented June4, 1946 REMOVAL or HrnnoGEN nALmEs FnoM Y nrnnocAnBoN CONVERSION rnonUors Gordon B. Zimmerman, Chicago, lll., assigner to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application July 5, 1943, Serial No. 493,500".

l Claims. (Cl. m50-683.5)

,The present invention relates to the removal of hydrogen halides from the reaction products of hydrocarbon conversion processes in which a. hydrogen halide is employed.

Broadlyl speaking, this invention is applicable to hydrocarbon conversion processes wherein a hydrogen halide is employed as a promoter in aV catalytic reaction or as a treating agent and is subsequently removed from the reaction products. The invention is particularly applicable to hydrocarbon conversion processes such as isomf erization and alkyla'tion wherein a catalyst of the Friedel-Crafts type is employed and hydrogen halide is introduced into,the reaotionzone to promote the action of the catalytic material.-

In one broad aspect, the present invention consists of a process for the removal of hydrogen halide from the reaction products of a hydrocarbon conversion process employing a hydrogen halide therein which comprises fractionating the reaction products to separate therefrom a major portion of the hydrogen halide from the hydrocarbon, separating the remaining portion of the original mixture into a fraction containing the converted hydrocarbons and substantially all of the remaining hydrogen halide and a fraction containing the unconverted hydrocarbons, and treating the former fraction to remove the hydrogen halide therefrom.

In various hydrocarbon conversion processes such as isomerization or alkylation' or paramns employing a Friedel-Crafts type catalyst promoted by a hydrogen halide, it is extremely difcult to produce a conversion product substantially free of hydrogen halide due primarily to the solubility of the hydrogen halide in the hydrocarbon product. It is ordinarily necessary to neutralize the hydrogen halide by washing with some treating agent such as caustic. However, this entails the I use of large treating equipment, large amounts of treating agents such as caustic with a high consumption of the treating agent by their reaction of a hydrogen halide with the caustic. A considerable amount of the hydrogen halide is also consumed by the' treating operation which further increases the cost of the conversion process. By employing the process of my invention, the hydrogen halide removal problem is simpliiied to a considerable extent. A major portion of the hydrogen halide is removed by fractionation prior to theftreating operation and is recycled to the 'I'he quantity of hydrocarbon which must be treated to remove hydrogen halide is limited to that obtained asv the final the conversion reaction.

product of The operabllity of the present invention to hydrocarbon conversion processes is more clearly evident from the description of the accompanying drawing which illustrates in conventional side elevation one type of invention may be applied.

For the sake of simplicity, the description of the drawing is limited to a process wherein normal butane is isomerized to lsobutane by contact with a catalyst comprising aluminum chloride in the presence of hydrogen chloride. However, it is not intended that this description place any4 undue limitations on the :broad application of this invention.

Referring to the drawing, normal butane is introduced to line i containing valve 2 into pump 3 which discharges through line 4 containing valve 5 through a bed of granular aluminum chlo` ride disposed within aluminum chloride supply tower 6.

A suilclent amount of aluminum chloride necessary to promote the isomerization of normal butane in a subsequent reaction zone is dissolved- .in the normal butane during its passage through the bedof granular aluminum chloride in supply tower 6. The temperature at which supply tower 6 is maintained will control the solubility of aluminum chloride and will vary depending upon the amount of catalyst desired in the subsequent reaction zone. This temperature will ordinarilybe Y within the range of from about 50 to about 300 F. and more preferably within the range of about 150 to 250 F. The pressure within tower 6 will vary depending upon the temperature but will be suilicient to maintain the normal butane in substantially liquid phase. The effluent from tower 6 passes through line l containing valve 8 and is commingledrwith hydrogen chloride introduced as hereinafter set forth within reactor 9 wherein a substantial portion of the normal butane charge is converted into isobutane.

Reactor 9 may comprise a large cylindrical chamber filled with a, suitable packing material `such as Raschig rings, quartz chips, granular alumina, activated charcoal and various other 'packing materials well known to those skilled in the art.

The temperature within reactor 9 will be dependent to some extent upon the hydrogen chloride concentration in the reaction mixture but will ordinarily be within the range of about 50" to 300 F. and more preferably within the range ofabout tc 250 F. The hydrogen chloride con :entration 'within reactor 9 will ordinarily be,

less than. 40 mol per cent of the normal butane process in which the charge and more preferably within the range of about 2 to 20' mol per cent of the charge. The pressure within reactor 9 may vary from substantially atmospheric to about 1000 pounds per square inch. The reaction may be satisfactorily conducted in either the liquid, vapor or mixed phase.

As a result of numerous side reactions which occur simultaneously with the isomerization reaction, some liquid hydrocarbon aluminum chloride complex is formed in reactor 9. This complee; passes down through the packing 4material and is trapped in the conical bottom section of reactor 9 and is periodically withdrawn through line I9 containing valve II and recovered as a product of the reaction.

The hydrocarbonv stream consisting of isobutane, unconverted normal butane and higher boiling hydrocarbons and containing aluminum chlo1 ride and hydrogen chloride is withdrawn through line I2 containing valve I3 and introduced into aluminum chloride column I4 wheryeinpit is fractionated to separate an overhead product containing most of the hydrogen chloride, unconverted normal butane and substantially all of the isobutane. This overhead product is introduced into hydrogen chloride stripper I1 from aluminum chloride tower I4 through line I5 containing valve I9. In hydrogen chloride stripper I1, a major prtion of the hydrogen chloride is separated from the hydrocarbons and withdrawn overhead through line I8 containing valve I9 into pump which discharges through line 2| containing valve 22 into line 1 and commingled with the normal butane as previously set forth. The hydrocarbons containing only a small amount of hydrogen chloride are withdrawn through line 23Y containing valve 24 and introduced into the de.

isobutanizer 25 wherein most of the isobutane'. and hydrogen chloride are Vseparated from the unconverted normal butane. The separated isobutane containing small amounts of hydrogen chloride is withdrawn-from de-isobutanizer 25 through line 29 containing valve 21 and introduced into scrubber 28 wherein it is contacted with a caustic solution to remove the hydrogen chloride therefrom. The isobutane stream substantially free of hydrogen chloride is withdrawn through line 29 containing valve 30 cooled and recovered as a product'of the reaction.

The Ct higher boiling hydrocarbons separated in -tower I4 and containing most of the aluminum chloride introduced into said tower through line I2 is withdrawn through line 35 into line 91 containing valve 9 9 into pump 39 which discharges through line 40 containing valve 4I into ,line 41 through which it is recycled to reactor 9.l In separating the Ca and higher boiling hydrocarbons from the isobutane, hydrogen chloride and unconverted normal butane introduced into aluminum chloride column I4, a suiilcient amount of unconverted normal butane is retained in the bottom fraction to provide sumcient liquid to dissolve substantially all oi' the aluminum chloride introduced into column I4. This method oi' operation permits therecycling of the aluminum chloride to the'reaction zone without any. of the operating difllculties ordinarily` encountered when attempting to handle mixtures of aluminum chloride in hydrocarbons. By maintaining a' sufficient amount of liquid to dissolve substantially all of the aluminum chloride "under the conditions at which the fractionation is conducted, the deDO- sition of aluminum chloride in the reboiles and subsequent equipment is eliminated` Y 4 To prevent a build-up of' C and heavier hy- `drocarbons in the system, a small amount is withdrawn through valve 39 into scrubber 28 wherein the aluminum chloride dissolved therein is removed by caustic wash. The Cs hydrocarbons are then recovered along with the isobutane fraction withdrawn through line 29 containing valve 30 and may be separated from isobutane in subsequent fractionating equipment if so desired.

The unconverted normal butane separated from the isobutane in de-isobutanizer 25 is withdrawn through line 42 containing valve 43 into pump 44 which discharges through line 45 containing valve 4'6 into line 4 through which it is recycled s to the aluminum chloride supply tower. A portion of this stream may be by-passed around the aluminum chloride supply tower through line 41 containing valve 49 into line 1.

The hydrogen chloride used ln starting the operation and any additionalAmake-up needed during the operation is introduced 4through line 49 containing valve 50 into pump 5I which discharges through line 52 containing valve 53 into line I9. 'I'he caustic is introduced in scrubber 38 throughline 3| containing valve 32 and is withdrawn through line 33 containing valve 34.

The removal of the hydrogen chloride may also be accomplished by the use of other suitable liquid treating agents such as sodium phosphate or solid absorbents vsuch as activated charcoal, bauxite, silica gel, etc.

I claim as my invention:

l. In the process of isomerizing normal butane wherein the normal butane is contacted with a metal halide catalyst in the lpresence of a hydrogen halide and the latter as well as some of the catalyst is removed from the zone of reaction along with the reaction products, the method of recovering the reaction products substantially free fractionating the reaction products to separate a C4 fraction containing the hydrogen halide from a heavier hydrocarbon fraction formed in the process containing the metal halide catalyst,l separating the bulk of the hydrogen halide from the C4 fraction by fractionation, further fractionating the C4 fraction to separate an isobutane fraction, containing the remainder of the hydrogen halide, from the unconverted normal butane, returning the normal butane and at least a portion of said heavier hydrocarbon fraction to the isomerizationv step, combining the isobutane fraction with the remainder of said heavier fraction and subjecting the mixture to caustic treating to remove the hydrogen halide and. metal 3. An isomerization process which comprises f isomerizing a paraln hydrocarbon ina reaction zone in the presence of a metal halide catalyst and 'a hydrogen halide promoter for said catalyst; fractionating the efiiuent reaction products to separate a relatively -low boiling fraction com prising isomerized paramn, unconverted paraffin,

and hydrogen halide from a higher boiling iracn tion comprising heavier hydrocarbons'formed during the reaction and dissolved metal halide catalyst; further fractionating said low boiling fraction to separate the bulk of the hydrogen halide therefrom and recyclingthe separated hydrogen halide to said reaction zone; further fractionating the remainder of said low boiling fracti :n to'sep- Y,

of hydrogen halide and catalyst which comprises l anital said isomerized paramn from said unconverted paramn; recycling said unconverted par,- amnand a. portion of said higher boiling fraction to said reaction zone; and introducing the separated isomerized paraiiin and the remainder of said higher boiling fraction into a treating zonev and therein effecting complete removal of hydrogen halide and metal halide from the hydrocarbons by reaction with a caustic solution.

5 hydrocarbon to be isomerized comprises normal` butane.

GORDON B. ZIMMERMAN. 

